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THE  CONNECTICUT  HOv  |  ::f  ^ 

AGRICULTURAL  EXPERIMENT  STATION 

NEW  HAVEN,  CONN. 


BULLETIN  171,  MAY,   1912. 


CORRELATION  AND  INHERITANCE 
IN  NICOTIANA  TABACUM. 


By  H.  K.  Hayes. 


TABLE   OF  CONTENTS. 

Page 

Introduction 3 

The  Material  Used 4 

The  Methods  Used 5 

Correlation  of  Parts 6 

Inheritance  of  Characters 7 

Family  (405  x  400) 8 

Family  (403  x  401) 10 

Family  (402  x  405) 19 

Summary  of  Results 26 

Interpretation  of  Results 27 

Conclusions 34 

Suggestions  to  the  Economic  Plant  Breeder 35 

Literature  Cited i 36 

Tables 37 


The  Bulletins  of  this  Station  are  mailed  free  to  citizens  of  Connecticut 
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CoDnecticBt  AiricDltiral  Eiperient  Statioi. 

OFFICERS     AND     STiVKK 


BOARD  OF  CONTROL. 

His  Excellency,  Simeon  E.  .Baldwin,  Ex  Officio,  President. 

Prof.  H.  W.  Conn,    Vice  Presiden* Middletown 

George  A.  Hopson,  Secretary Wallingford 

E.  H.  Jenkins,  Director  and   Treasurer      ........     New  Haven 

J.  W.  Alsop Avon 

W.  H.  Lee .     Orange 

Frank  H.  Stadtmueller Elmwood 

James  H.  Webb      Hamden 


Administration 


STATION  STAFP\ 

E.  H.  Jenkins,  Ph.  D.,  Director  and   Treasurer. 

Miss  V.  E.   Cole,   Librarian  and  Stenographer. 

Miss  L.  M.  Brautlecht,  Bookkeeper  and  Stenographer. 


Chemistry. 

Analytical  Laboratory. 


John  Phillips  Street,  M.  S.,  Chemist  in  Charge. 
E.   Monroe  Bailey,  Ph.   D.,  C.  B.   Morrison,  B.  S. 
R.  B.  Roe,  A.  B.,  C.  E.  Shepard,  Assistants. 
Hugo  Lange,  Laboratory   Helper. 
V.  L.  Churchill,  Sampling  Agetit. 


Proteid  Research. 


T.   B.  Osborne,  Ph.  D.,  Chetnist  in  Charge. 
Miss  E.  L.  Ferry,  A.  B.,  Assistant. 
Miss  Luva  Francis,  Stenographer. 


Botany. 


G.  P!  Clinton,  S.  D.,  Botanist. 

E.  M.  Stoddard,  B.  S.,  Assistant. 

Miss  M.  H.  Jagger,  Seed  Analyst. 

Miss  E.  B.  Whittlesey,   Hebarium  Assistant. 


Entomology. 


W.  E.  Britton,  Ph.  D.,  Entomologist;    also  State 

Entomologist. 
B.  H.  Walden,  B.  Agr.,  D.  J.  Caffrey,  B.  S., 
H.  B.   Kirk,   Assista7its. 
Miss  E.  B.  Whittlesey,  Stenographer. 


Forestry. 


Samuel  N.  Spring,  M.  F.,   Forester;    also  State 

Forester  and  State  Forest  Fire  Warden. 
W.  O.  Filley,   Assistatit  State  Forester. 
Miss  E.  L.  Avery,  Stenographer. 


Plant  Breeding. 


H.  K.  Hayes,  M.  S.,  Plant   Breeder. 
C.  D.  Hubbell,  .Assistant. 


Buildings  and  Grounds. 


William  Veitch,  In   Charge. 


■^ 


CORRELATION  AND  INHERITANCE 
IN  NICOTIANA  TABACUM. 


H.  K.  Hayes. 


INTRODUCTION. 


The  objects  of  this  paper  are  two  fold;  first,  to  give  some  new 
facts  regarding  the  correlation  and  inheritance  of  plant  charac- 
ters in  Nicotiana  tabacum,  second,  to  show  how  these  facts  may 
be  applied  by  plant  breeders  to  the  production  of  new  improved 
forms. 

The  following  facts  show  that  Nicotiana  tabacum  offers 
special  facilities  for  the  study  of  the  correlation  and  inheritance 
of  plant  characters. 

1.  There  are  a  large  number  of  different  varieties  which 
present  easily  measured  quantitative  differences  in  characters. 

2.  The  Nicotiana  tabacum  forms  are  naturally  close  polli- 
nated and  can  be  inbred  for  many  years  without  deterioration. 

3.  The  technique  of  crossing  is  very  simple  and  a  large 
number  of  seeds  may  be  produced  by  a  single  cross. 

4.  The  seed  is  viable  for  a  long  time  so  that  a  considerable 
number  of  generations  may  be  grown  on  the  same  field  in  one 
year. 

As  tobacco  is  one  of  the  principal  agricultural  crops  of  the 
United  States  it  is  very  important  that  all  of  the  facts  regarding 
the  correlation  and  inheritance  of  its  characters  should  be  known. 
For  the  last  nine  years  many  attempts  have  been  made  to  pro- 
duce improved  forms  by  hybridization  without  a  very  definite 
knowledge  of  the  underlying  principles.  It  is  hoped  that  this 
paper  may  be  a  contribution  to  this  knowledge. 


4  INHERITANCE  IN  NICOTIANA  TABACUM. 

THE    MATERIAL   USED. 

The  material  used  for  the  studies  reported  in  this  paper,  with 
the  exception  of  the  Broadleaf  strain,  consisted  of  types  which 
had  been  inbred  for  a  number  of  years  and  which  were  uniform 
to  type.  These  were  Havana  and  Broadleaf,  which  have  been 
grown  in  Connecticut  for  cigar  wrappers  for  many  years,  and 
three  A^arieties  for  growing  under  shade,  which  had  been  grown 
in  row  selections  for  a  number  of  years  from  selfed  seed  by  The 
Connecticut  Agricultural  Experiment  Station  in  cooperation 
with  the  United  States  Department  of  Agriculture. 

Following  is  a  short  description  of  the  forms  used  in  the 
experiment.  Statistical  determinations  of  special  characters- 
are  given  later. 

No.  400.     Uncle  Sam  Sumatra. 

This  type  proved  to  be  of  little  practical  value  for  growing 
under  shade  because  the  leaves,  when  cured,  had  a  papery 
texture.  The  number  of  leaves,  counting  from  the  fourth  leaf 
from  the  bottom  to  the  leaf  below  the  bald  sucker*,  ranges 
from  seventeen  to  twenty-five  and  averages  about  twent^^-two. 

No.  401.     Broadleaf. 

A  variety  which  has  been  cultivated  in  the  open  since  the 
early  history  of  the  tobacco  industry  in  Connecticut.  The 
number  of  leaves  ranges  from  sixteen  to  twenty-two  and  averages 
nineteen.  The  average  height  is  about  fifty-five  inches  and 
the  average  leaf  area  is  about  9  sq.  dcms.  Its  leaves  are 
drooping  in  habit. 

No.  402.      Havana. 

Another  Connecticut  out-door  variety,  which  averages  about 
twenty  leaves  per  plant,  with  a  range  of  from  sixteen  to  twent}— 
five.  The  average  height  is  fifty-six  inches  and  average  leaf 
area  7  sq.  dcms.  Its  leaves  are  more  erect  than  the  Broadleaf 
and  droop  slightly  at  the  tip. 

No.  403.     Small-leafed  Sumatra. 

This  type  was  introduced  for  shade  purposes,  but  did  not 
prove  so  satisfactory  as  the  Cuban.     It  averages  about  twenty- 


*  The  "bald  sucker"  is  a  farm  name  for  the  last  sucker  or  flowering 
stem  on  the  top  of  the  plant  which  has  no  true  leaves. 


THE  METHODS  USED.  5 

•seven  leaves  per  plant  with  a  range  from  twenty-three  to  thirty- 
one.  The  average  height  is  about  seventy-six  inches  and  the 
average  leaf  area  is  about  3  sq.  dcms.  The  leaves  are  erect 
in  habit. 

No.  4-05.     Cuban. 

This  type  is  now  used  for  growing  under  shade  in  Connecticut, 
■over  two  thousand  acres  being  raised  in  the  valley  in  1911. 
It  has  a  range  of  from  sixteen  to  twenty-five  leaves  and  averages 
about  twenty.  The  average  leaf  area  is  about  5  sq.  dcms.  and 
average  height  about  sixty-five  inches. 

THE    METHODS    USED. 

As  shown  by  the  descriptions,  each  type  has  been  given  a 
number.  A  cross  between  No.  405,  Cuban,  and  No.  402,  Havana, 
has  been  written  (405x402),  the  female  parent  coming  first. 
Whenever  later  generations  have  been  grown  they  have  been 
noted  by  further  numbers,  as  402-1,  (405  x  402)-l,  which  denote 
respectively  the  second  generation  of  Havana  and  the  second 
generation  of  the  cross  between  Cuban  female  and  Havana  male. 
The  tobacco  flower  is  naturally  arranged  for  self-fertilization. 
If  inbred  seed  is  desired  it  is  only  necessary  to  cover  the  flower 
cluster  with  a  Manila  paper  bag;  the  12  lb.  size  having  been 
found  to  be  most  satisfactory  for  this  purpose.  It  is,  however, 
•advisable  to  take  off  all  but  about  twenty  of  the  seed  pods, 
as  these  will  produce  an  abundance  of  seed. 

The  technical  work  in  crossing  two  varieties  of  tobacco  is 
very  simple.  The  corolla  is  split  up  one  side,  before  the  blossom 
•opens,  and  the  stamens  are  removed.  Pollen  from  another 
variety  (taken  from  its  stamens  by  means  of  a  scalpel  or  other 
sharp  instrument)  is  applied  to  the  pistil  of  the  variety  from 
which  the  stamens  have  been  removed.  Those  blossoms  not 
used  in  crossing  are  removed  and  the  seed-head  covered  with  a 
Manila  paper  bag. 

The  following  characters  were  studied  with  reference  to 
correlation  and  inheritance. 

1.  Number  of  leaves  per  plant.  The  number  was  counted 
from  the  fourth  leaf  from  the  bottom  of  the  plant  to  the  leaf 
just  below  the  bald  sucker  at  the  top,  which  gives  about  .the 
number  that  is  usually  harvested. 


6  INHERITANCE  IN  NICOTIANA  TABACUM. 

2.  Height  of  plant  measured  from  the  ground  to  the  last 
leaf  counted. 

3.  Average  area  of  leaves.  After  the  plants  had  reached 
maturity,  tracings  of  the  fourth  leaf  from  the  bottom,  the 
middle  leaf  and  the  last  leaf  below  the  bald  sucker  were  made 
on  smooth  paper  and  each  was  given  a  series  number.  The 
area  of  each  tracing  was  determined  with  a  planimeter  which 
gives  an  experimental  error  of  only  about  5  sq.  centimeters 
per  leaf.  The  term  "average  area  of  leaf"  is  the  average  area 
of  these  three  separate  leaves. 

4.  Average  length  of  midrib,  which  is  the  average  length 
of  the  three  leaves  used  for  the  area  measurements. 

5.  Average  width  of  leaf,  taken  in  the  same  manner  as  the 
length  measurements. 

The  data,  with  one  exception,  which  will  be  mentioned  later, 
were  all  taken  in  a  uniform  manner  by  the  author  and  Air. 
C.  D.  Hubbell.  The  planimeter  measurements  were  made  by 
Mr.  Hubbell,  who  has  given  much  efficient  assistance  in  this 
work.  We  wish  also  to  express  our  thanks  to  Dr.  E.  M.  East 
for  much  helpful  advice  and  cooperation. 

CORRELATION   OF    PARTS. 

The  question  of  correlation  between  parts  is  of  great  im- 
portance when  applying  the  principal  of  selection  to  improve- 
ment of  plants.  In  our  work  the  usual  correlation  table  has 
been  used  and  the  coefficient  of  correlation  determined.  The 
coefficient  of  correlation  shows  the  degree  of  mutual  relation, 
between  the  characters  in  question.  It  it  is  low  (i.  e.,  much 
below  0.50)  it  indicates  that  they  do  not  depend  very  much  upon 
each  other;  if  high,  it  indicates  that  they  are  closely  related 
and  when  it  rises  to  unity  it  shows  that  both  characters  depend 
upon  the  same  cause  and  are  inherited  together.  If  two  genes 
are  located  in  the  same  chromosome  as  supposed  by  Emerson  ( :11) 
they  could  be  inherited  together  but  not  depend  on  the  same 
cause. 

Two  types  were  used  to  study  the  correlation  between  parts. 
Correlation  tables  of  the  results  are  given  at  the  end  of  this 
paper.  For  convenience  in  discussing  results,  the  dift'erent 
coefficients  of  correlation  are  here  grouped  in  tabular  form. 


INHERITANCE  OF  CHARACTERS. 


TABLE  I. 

COMPARISON    OF    CORRELATION   COEFFICIENTS. 


No. 

Correlation 
between  no.  of 

leaves  and 
hght.  of  plant 

Correlation 
between  no.  of 

leaves  and 
aver,  leaf  area 

Correlation 

between  length 

and  breadth 

of  leaf 

No.  401  Broadleaf 
No.  403  Sumatra 
(403  X  401  )F, 
(403x401)-lF2 
(403  X  401)-4F2 

+.368  ±.048 
+.631  ±.033 
+  .406  ±.046 
+  .342  ±.058 
+  .408  ±.036 

-.165  ±.054 
-.008  ±.055 
-.226  ±.052 
-.124  ±.065 
-.076  ±.043 

+  .684  ±.029 
+  .497  ±.041 
+  .818±.018 
+  .737  ±.030 
+  .761  ±.018 

The  above  table  shows  that  the  crosses  between  the  Nos. 
401  and  403  have  not  apparently  affected  the  mutual  relation- 
ship of  the  different  characters  studied.  Thus,  while  there  is 
a  positive  correlation  between  the  number  of  leaves  per  plant 
and  total  plant  height,  this  correlation  as  a  rule  is  somewhat 
less  than  +0.5  in  our  tests.  One  might  expect  some  correlation 
between  the  height  and  number  of  leaves  because  the  former 
is  the  combined  length  of  the  internodes,  and  the  number  of 
internodes  depends  on  the  number  of  leaves.  But  the  corre- 
lation is  not  very  large  and  shows  no  very  close  relation  between 
height  and  number  of  leaves. 

There  is  a  small  negative  correlation  of  leaf  area  and  number 
of  leaves  but  the  relation  between  the  two  is  so  small  as  to  have 
no  practical  value.  That  is,  number  of  leaves  is  not  a  character 
distinctly  opposed  to  leaf  area. 

The  high  correlation  between  length  and  breadth  of  leaf 
indicates  that  both  are  very  closely  related,  that  is,  that  both 
are  dependent  on  the  same  cause  or  series  of  causes  in  inheritance. 

INHERITANCE    OF    CHARACTERS 

While  all  of  the  characters  studied  show  fluctuating  varia- 
bility they  are  very  differently  affected  by  environment.  The 
most  uniform  character  of  all  was  the  number  of  leaves  per 
plant,  which  was  little  affected  unless  the  conditions  were 
so  unfavorable  as  to  greatly  stunt  or  dwarf  the  growth  of  the 
plant,  as  appears  in  the  following  table.  Each  of  these  four 
selections  was  grown  at  Forest  Hills,  Massachusetts,  Bloomfield, 
Connecticut,  and  New  Haven,  Connecticut,  from  seeds  of  a 
single    plant.     The    Forest    Hills   plants   were   grown    and    the 


8  INHERITANCE  IN  NICOTIANA  TABACUM. 

data  taken  by  Dr.  E.  M.  East.     The  calculated  mean  is  used  to 
determine  the  value  of  the  selection. 

TABLE  II. 

NUMBER  OF  LEAVES  PER  PLANT. 


Selection 

Forest  Hills 

Bloomfield 

New  Haven 

Average 
Mean 

1 
2 
3 
4 

25.8  ±.091 
30.8±.115 
25.3  ±.085 
25.8  ±.091 

25.7  ±.081 
29.6  ±.078 
25.2  ±.074 
27.4  ±.079 

25.2  ±.077 
30.7^.090 
24.7  ±.073 
26.7  ±.078 

25 . 6 
30.4 
25.1 
26.6 

The  field  at  Forest  Hills  was  fairly  fertile  but  in  a  region 
where  tobacco  is  never  grown  commercially.  Bloomfield  is  in 
the  center  of  the  tobacco-growing  region  and  the  soil  is  per- 
fectly adapted  to  it  and  heavily  fertilized.  The  soil  at  New 
Haven  is  a  thin,  poor,  sandy  loam  only  moderately  dressed  with 
manure  and  chemicals. 

The  means  of  the  different  selections  compared  with  the 
average  mean  show  a  variation  of  only  ±0.8  leaves,  and  as  only 
about  one  hundred  plants  were  counted  for  each  determination 
the  results  seem  very  uniform. 

Three  crosses  have  been  studied  as  to  inheritance  of  charac- 
ters and  for  convenience  each  will  be  considered  separately. 

Family  {If-Oo  x  JfOO)  Ctthan  x  Uncle  Sam  Sumatra. 

This  cross  was  made  in  1907,  the  reciprocal  Fi  generations 
and  the  parents  were  grown  in  1908,  and  the  F-  generations  of 
the  crosses  and  parents  in  1909.  In  both  years  the  crosses 
and  parents  grew  on  the  same  plot  under  shade  and  therefore 
under  uniform  conditions.  The  data  given  in  Table  3.  show 
the  range  of  variation,  the  number  of  plants  studied  and  the 
usual  statistical  determinations  which  consist  of  the  Mean,  A, 
the  Standard  Deviation,  S.  D.,  and  the  Coefficient  of  Varia- 
bility, C.  V.  The  plants  were  not  topped  as  uniformly  in  1908 
as  with  the  later  generations  and  therefore  the  number  of 
leaves  per  plant  cannot  be  accurately  compared  with  the  numbers 
in  later  years.  This  3"ear's  work,  however,  shows  that  there 
was  no  increase  in  variability  as  determined  b}'  C.  V.  due  to 
\\ie  crossing. 


>• 

o 

6. 08  ±.276 
5.  51  ±.215 
6 . 77  ± . 234 
6. 97  ±.271 
4. 62  ±.186 
5. 64  ±.218 
8.10±.315 
8.56±.333 

d 

in 

1  . 03  ± . 047 
1 . 08  ± . 042 
1 . 28  ± . 044 

1 . 52  ± . 059 
0.85  ±.029 
1.01  ±.039 

1 . 53  ± . 060 
1.66  ±.065 

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10  INHERITANCE  IN  NICOTIANA  TABACUM. 

The  second  generation  of  the  parents  was  grown  in  each  case 
from  single  inbred  plants  of  the  preceding  year.  The  F2  gener- 
ations of  the  crosses  were  grown  from  a  mixture  of  seed  from 
several  inbred  plants  of  Fi. 

The  range  of  variability  as  shown  by  C.  V.  is  considerably 
greater  for  the  F2  generation  of  the  crosses  than  for  the  parents. 
As  seed  from  several  plants  was  used  for  the  F2  generations 
this  increased  variability  might  be  considered  to  be  due  to 
gametic  differences  in  the  different  parent  plants,  but  it  seems 
to  us  more  reasonably  explained  by  a  recombination  of  charac- 
ters. Although  no  statistical  results  can  be  given,  it  is  onl}^ 
fair  to  state  that  the  F2  generations  also  showed  a  range  of 
types  which  were  more  or  less  like  one  or  the  other  parent  and 
intermediates  between  them. 
Family  {403  x  4OI ) ,  Sumatra  x  Broadleaf. 

This  cross  was  made  in  1910.  These  same  selections  and  the 
Fi  and  F2  generations  were  the  types  used  for  the  discussion  of 
correlation  between  parts  given  above.  It  should  be  remem- 
bered that  the  correlation  between  number  of  leaves  and  height 
of  plant  was  somewhat  less  than  +0.5,  that  in  all  cases  there 
was  a  small  negative  correlation  between  average  area  of  leaf 
and  number  of  leaves  but  so  small  as  to  have  little  significance, 
and  that  there  was  a  large  correlation  between  length  and  breadth 
of  leaf.  It  is  also  important  to  know  that  the  crossing  showed 
little  influence  on  the  correlation  coefficient. 

In  the  consideration  of  inheritance  of  special  characters, 
each  character  will  be  discussed  separately. 

Tables  IV  and  V  give  in  consecutive  arrangement  from  left  to 
right,  the  selecting  number,  the  place  grown  (C.  denoting 
Centerville,  Connecticut,  and  B.  Bloomfield,  Connecticut),  the 
year  grown,  in  Table  IV  the  parental  number  of  leaves  when 
known,  the  total  number  of  variates  and  the  usual  statistical 
determinations. 

As  both  tables  give  results  from  the  same  parent  plants  the 
following  discussion  applies  equally  well  to  both.  The  seed- 
lings in  all  cases  were  started  in  sterilized  soil  and  every  pre- 
caution was  taken  to  prevent  mixture  of  seeds.  Seedlings 
for  the  Centerville  selections  were  grown  in  the  greenhouse, 
while  the  Bloomfield  selections  were  grown  under  glass  in  seed- 
beds at  Bloomfield.     The  Fi  generation  and  the  parent  selec- 


INHERITANCE  OF  CHARACTERS.  11 

tions  were  grown  in  consecutive  rows  at  Centerville  in  1910 
and  the  plants  were  uniformly  spaced  on  the  row. 

The  range  of  variation  for  number  of  leaves  per  plant,  Table 
IV,  is  not  transgressive  and  the  Fi  generation  shows  an  intermed- 
iate condition.  The  Mean  for  number  of  leaves  of  No.  403, 
Sumatra,  is  28.2 ±.082,  for  No.  401,  Broadleaf,  is  19.2 ±.053, 
thus  giving  an  average  Mean  of  23.7  leaves  for  the  parents. 
The  Mean  of  the  Fi  generation  was  23. 6 ±.072,  which  is  very 
nearly  the  same  as  the  average  of  the  parents.  The  variability, 
as  determined  b}^  C.  V.,  is  about  the  same  for  the  Fi  and  parent 
types.  The  Fi  plants  could  be  distinguished  from  either  parent 
by  anyone  who  was  familiar  with  the  habits  of  the  varieties 
used. 

In  1911  the  second  generation  of  the  parents  and  some  F2 
generation  crosses  were  grown,  the  parents  at  Centerville  and 
the  F^  crosses  both  at  Centerville  and  Bloomfield.  The  season 
was  a  very  dry  one,  especially  near  New  Haven,  and  as  the 
Centerville  plot  was  on  a  poor  gravelly  soil  the  plants  were 
somewhat  stunted.  The  range  of  variation  of  the  parent 
types  was  about  the  same  as  in  1910,  although  the  Mean  of 
No.  403,  Sumatra,  was  decreased  from  28. 2 ±.082  to  26. 5 ±.106. 

The  parents  of  the  F2  generation  crosses  No.  (403x401)-l, 
No.  (403  X  401) -3  and  (403  x  401)-4  represented  some  of  the  wider 
ranges  of  variation  of  the  Fi  generation  in  number  of  leaves 
and  plant  height.  These  three  selections  were  each  grown 
from  single  inbred  plants  of  the  Fi  generation  and  in  1911  were 
grown  at  Bloomfield  on  a  normally  fertilized  tobacco  soil,  all 
giving  similar,  results.  The  range  of  variation  of  these  F2 
selections  was  as  great  as  that  of  the  combined  parental  and 
Fi  generations.  These  results  are  considered  very  conclusive, 
as  a  total  of  5,992  plants  were  counted.  The  field  was  badly 
infested  with  cut  worms  and  was  reset  three  different  times, 
thus  using  seedlings  of  different  ages  and  rate  of  development 
in  the  bed  and  giving  a  high  probability  that  the  plants  were 
representative  of  the  whole  F2  generation. 

Two  of  the  F2  generations  grown  at  Bloomfield  were  also  grown 
at  Centerville.  Thus  we  have  an  opportunity  to  observe  the 
effects  of  a  normal  and  of  a  poor  environment  on  plants  grown 
from  seed  of  single  inbred  plants.  The  range  of  variation  at 
Centerville,  considering  the  number  of  plants  grown,  proved  to 


12  INHERITANCE  IN  NICOTIANA  TABACUM. 

be  about  the  same  as  for  the  F2  generations  at  Bloomfield  and 
similar  Means  for  leaf  number  were  obtained.  Comparing^ 
the  variability  of  the  F2  generations  with  the  parents  and  Fi 
we  find  an  increase  of  from  40  to  50%. 

Table  V,  which  gives  the  heights  of  plants  in  three-inch 
classes,  shows  also  an  intermediate  condition  in  Fi  for  plant 
height  and  no  increase  of  variability^  due  to  crossing.  The- 
Mean  of  the  Fi  generation,  70. 8 ±.250,  is  somewhat  larger  than 
that  of  the  average  of  the  parents,  which  is  65.55.  This  is 
not  due,  however,,  to  dominance,  but  to  increased  Aagor  due  to 
hybridization  and  as  this  matter  has  been  discussed  in  a  pre- 
vious publication  it  will  receive  no  further  attention  here. 

The  comparison  of  the  effects  of  poor  and  normal  euAdron- 
ment  on  plant  height  gives  somewhat  dift'erent  results  than 
for  the  number  of  leaves  per  plant.  In  number  of  leaves 
per  plant  and  also  in  height  of  plant  there  is  a  slight  increase 
in  S.  D.,  in  three  of  the  four  cases,  due  to  poor  enAdronment. 
In  the  fourth  case,  however,  in  which  only  107  plants  were- 
grown,  there  is  a  large  increase  in  C.  V.  for  plant  height  due  to 
poor  environment.  The  coefficients  of  variability  for  the- 
number  of  leaves  are  not  appreciably  affected.  These  few  data, 
accord  with  Love's  (:11)  conclusion  that  some  characters  of  a 
species  or  variety  are  more  variable  than  others.  Our  results. 
are  given,  however,  to  show  to  what  an  extent  the  statistical 
determinations  can  be  relied  upon  when  diff'erent  environmental 
conditions  are  used  for  the  different  generations.  The  classes- 
and  frequencies  are  given  in  our  tables  for  all  characters,  which 
affords  a  much  better  opportunity  to  discover  the  range  of 
variation  than  where  only  the  statistical  determinations  are- 
shown.  There  is  no  doubt  that  plant  height  shows  a  greater 
variation  in  F2  and  that  this  is  due  to  crossing  of  different  t^'pes. 
While  there  is  room  for  differences  of  opinion  as  to  the  cause,  it. 
seems  to  the  author  that  segregation  of  characters  supplies  the 
most  reasonable  interpretation.  It  is  realized,  however,  that 
until  the  F3  generation  is  grown  we  know  practically  nothing 
of  the  purity  of  these  F2  forms. 

Tables  VI,  VII  and  VIII  give  the  results  of  a  study  of  the  aver- 
age leaf  area,  the  average  width  and  average  length  of  leaf  respect- 
ively of  the  above  cross.  In  these  tables  the  parents  and  Fi 
were  grown  in  1910  and  the  F2  generations  in  1911.     These  are 


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INHERITANCE  OF  CHARACTERS.  15 

the  same  plants  which  were  used  to  study  the  plant  height 
and  number  of  leaves  shown  in  the  previous  tables. 

The  tobacco  plot  at  Centerville  in  1910  was  on  a  fairly  good 
soil  and  the  plants  made  a  normal  growth.  The  tables  show 
that  the  mean  of  the  Fi  generation  is  somewhat  larger  than  the 
average  of  the  parents.  This  is  believed  to  be  due  to  increased 
vigor  from  crossing  and  to  have  nothing  to  do  with  the  matter 
of  inheritance. 

The  F2  generation  consisted  of  two  selections.  The  range 
of  A^ariation  was  somewhat  larger  in  most  cases  than  in  Fi. 
Three  variates  in  average  width  of  leaf  were  obtained,  which 
were  as  small  as  the  extreme  small  A^ariates  of  No.  403.  In  F2 
there  were  no  variates  in  average  length  of  midrib  and  average 
leaf  areas  as  small  as  the  extreme  small  variates  of  No.  403, 
although  several  very  closely  approached  this  size.  The  possible 
increase  due  to  heterozygosis  seems  a  probable  explanation 
for  the  non-appearance  of  smaller  variates.  No  variates  were 
obtained  in  a  higher  class  than  the  extremes  of  the  Fi  gener- 
ation. The  season  was  very  unfavorable  which,  without 
doubt,  decreased  the  average  size  of  the  leaves.  It  is  regretted 
that  no  data  were  taken  for  leaf  characters  on  the  parent  varie- 
ties in  1911,  but  from  observation  it  is  safe  to  say  that  no  variates 
would  have  been  produced  in  as  large  classes  as  in  1910.  Another 
fact  which  may  partially  explain  the  small  variation  in  Fo  is 
the  small  number  of  plants  grown  (three  hundred  and  forty- 
eight)  . 

Results  obtained  from  a  few  plants  saved  from  the  Fo  Bloom- 
field  crosses  are  given  in  the  tables  under  the  heading,  "seed 
plants."  The  purpose  of  giving  the  data  on  these  few  plants 
is  to  show  that  nearly  as  large  average  leaf  areas  were  pro- 
duced in  the  Fo  crosses  as  in  the  larger  parent  and  that  the 
reason  that  no  such  extreme  variates  appeared  in  our  Center- 
ville cultures  is,  in  a  large  measure,  due  to  the  unfavorable 
einvironment. 

A  consideration  of  the  different  types  of  leaves  found  in 
the  Bloomfield  and  Centerville  fields  convinces  the  writer  that 
there  is  a  greater  variation  of  leaf  area  and  dimensions  in  F2 
than  in  the  parental  or  Fi  forms. 


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INHERITANCE  OF  CHARACTERS.  19 

Family  (402x405),   Havana  x  Cuban. 

This  cross  was  made  in  1909,  the  parent  varieties  and  the 
Fi  generation  were  grown  under  shade  at  Bloomfield,  Connecti- 
cut, in  1910,  and  the  F2  generation  with  the  parents  were  again 
grown  in  1911  on  the  same  shaded  field.  In  both  years  the 
season  was  favorable  for  shade  tobacco,  and  the  results  were 
not  iinpaired  by  unfavorable  environmental  influences.  The 
usual  precautions  were  taken  to  prevent  mixture  of  seed  and 
the  plants  were  evenly  spaced  on  the  rows.  Only  a  few  seed- 
lings were  destroyed  by  insects  or  other  causes  and  these  were 
reset  about  a  week  after  the  first  setting. 

The  Fi  generation  consisted  of  reciprocal  crosses,  but  as 
the  data  from  each  gave  similar  results  and  as  only  75  plants 
of  each  cross  were  grown  the  combined  results  are  given  under 
one  head.  In  our  experience  with  tobacco,  reciprocal  crosses 
have  always  yielded  like  results. 

Table  IX  gives  the  results  of  the  study  of  the  inheritance 
of  number  of  leaves  per  plant  for  this  family. 

The  Fi  generation  showed  about  the  same  range  of  variation 
as  the  parent  types,  the  Mean  for  the  parents  and  for  the  Fi 
generation  being  nearly  the  same.  Thus,  No.  405  Cuban  gave 
a  Mean  of  19.9 ±.082,  No.  402  Havana  gave  a  Mean  of  19.8 ± 
.076,  while  the  cross  (402x405)  had  a  Mean  of  19.8 ±.067. 
The  variability  as  determined  by  either  S.  D.  or  C.  V.  was  a 
little  less  for  the  cross  than  for  either  parent. 

The  F2  generations  of  the  cross  and  the  parent  generations 
were  grown  in  1911.  The  parent  types  in  each  case  had  an 
increase  in  the  Mean  over  the  previous  year  of  from  .5  to  .7  of 
a  leaf  per  plant,  respectively.  As  only  150  plants  were  grown, 
however,  it  is  impossible  to  tell  whether  this  is  due  to  a  slight 
impurity  in  the  parent  plants  or  to  some  other  factor.  The 
coefficient  of  variability  was  greater  for  the  parent  No.  402-1 
than  in  1910,  and  less  for  the  parent  No.  405-1.  The  second 
generation  of  the  cross  was  very  variable,  shewing  a  range  of 
from  14  to  33  leaves  per  plant  and  an  increase  of  approximately 
100%  in  variability  as  determined  by  either  S.  D.  or  C-  V. 
The  Mean  for  the  number  of  leaves  per  plant  was  also  greater 
in  Fa  than  in  Fi. 

Table  X  gives  the  results  of  the  study  of  plant  height.  The 
Mean  is  larger  in  Fi  than  in  either  parent.     The  Mean  of  No. 


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22  INHERITANCE  IN  NICOTIANA  TABACUM. 

405  Cuban  was  65.4 ±.264,  of  No.  402  Havana  was  56.5 ±.218, 
while  the  Fi  had  a  Mean  for  height  of  65. 5 ±.270.  This,  how- 
ever is  no  doubt  due  to  increased  vigor  from  crossing  and  has 
no  significance  in  inheritance.  The  variability  was  a  very  little 
larger  for  the  Fi  generation  than  for  either  parent  and  well 
within  the  probable  error  of  the  determinations. 

The  F2  generation  showed  an  increased  variability  and  a 
considerable  degree  of  correlation  between  height  of  plant  and 
number  of  leaves.  Thus,  a  correlation  table  gives  a  correla- 
tion coefficient  of  +.786 ±.023  for  number  of  leaves  and  plant 
height. 

As  Table  XI  proves,  selection  No.  405  Cuban  has  a  smaller 
leaf  than  No.  402  Havana,  although  the  range  of  variation 
is  very  much  the  same.  The  Fi  generation  showed  the  same 
range  of  variation  as  the  parent  No.  402,  although  the  Mean 
was  lower  for  the  cross.  The  variability  in  Fi  was  also  greater 
than  that  of  either  parent,  but  within  the  probable  errors. 

The  F2  generation  produced  some  leaves  with  as  small  average 
size  as  the  smaller  parent  and  some  leaves  which  averaged 
larger  than  either  parent.  The  variability  as  determined  by 
C.  V.  was  also  materially  greater  than  that  of  the  parents. 

The  correlation  coefficient  for  the  average  area  of  leaves 
and  number  of  leaves  per  plant  was  —.092 ±.048,  which  shows 
conclusively  that  there  is  very  little  correlation  between  number 
of  leaves  and  leaf  area  and  that  these  two  characters  are  inher- 
ited independently. 

Tables  XII  and  XIII  show  that  the  difference  of  the  parents 
in  size  characters  of  the  leaf  is  chiefly  a  difference  in  average 
length,  as  the  average  width  of  leaves  of  both  parents  is  very 
nearly  the  same. 

Table  XII  shows  that  the  range  of  variability  of  the  Fo  genera- 
tion for  length  of  midrib  is  as  great  as  the  combined  variability 
of  the  Fi  generation  and  the  parents.  One  variate  had  a  smaller 
average  length  of  leaf  than  the  lower  class  of  the  lower  parent, 
and  seven  variates  had  a  longer  average  midrib  than  the  larger 
parent. 

The  abrupt  ending  of  the  parent  classes,  however,  and  the 
fact  that  a  larger  number  of  variates  occurred  in  Fo  than  in 
the  parents  makes  it  probable  that  the  variability  for  average 


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26  INHERITANCE  IN  NICOTIANA  TABACUM. 

length  of  midrib  is  no  greater  for  F2  than  for  the  combined 
parent  and  Fi  generations. 

Table  XIII  shows  an  increased  variability  in  F2  for  average 
leaf  width,  although  the  parents  have  nearly  the  same  Alean 
and  range  of  variability.  This,  we  believe,  is  due  to  correlation 
between  width  and  length  of  leaf*  and  also  explains  w^hy  leaves 
yielded  by  F2  were  larger  than  those  of  the  larger  parent.  This 
explanation  seems  logical  in  view  of  the  fact  that  there  were  no 
leaves  with  a  smaller  average  area  than  that  of  the  smaller 
parent. 

SUMMARY    OF    RESULTS. 

A.  Correlation  of  Characters. 

1.  In  the  two  types  studied  and  in  the  first  and  second 
generation  of  crosses  between  them  there  was  a  positive  corre- 
lation between  number  of  leaves  and  height  of  plant  although 
in  all  but  one  case  this  was  less  than  +0.5. 

2.  The  number  of  leaves  and  average  leaf  area  showed 
only  a  slight  negative  correlation,  i.  e.,  a  large  number  of  leaves 
was  associated  with  a  slightly  smaller  average  leaf  area. 

3.  There  was  a  distinct  plus  correlation  between  length 
and  width  of  leaf,  i.  e.,  the  longer  leaves  were  on  the  average 
also  the  broader  ones. 

B.  Inheritance  of  Characters. 

1.  The  characters  studied  showed  very  different  fluctuating 
variabilities  due  to  environment.  The  most  uniform  charac- 
ter, in  this  respect,  was  number  of  leaves  per  plant,  which  was  little 
affected  unless  the  conditions  of  growth  greatly  stunted  or 
dwarfed  the  plant. 

2.  Reciprocal  crosses  are  equal  within  the  limits  of  fluctuat- 
ing variability. 

3.  The  Fi  generation  is  intermediate  in  the  characters 
studied,  being  as  a  rule  somewhat  larger  than  the  average  of 
the^  parents.  All  characters  studied  except  the  number  of 
leaves  per  plant  showed  added  vigor. 

4.  The  Fi  generation  is  no  more  variable  than  the  parents, 
the  variability  of  Fi  being  found  slightly  greater  than  the  average 


*  The  correlation  between  length  and  width  of  leaf  as  determined  by 
the  correlation  coefficient  proved  to  be  +.814  ±.016. 


INTERPRETATION  OF  RESULTS.  27 

of  the  parents  in  six  cases  and  less  in  five  cases.     This  result 
agrees  with  Johannsen's  (:07)  observation. 

5.  Different  variates  in  Fi  give  similar  results  m  F2,  showing 
that  the  variation  in  Fi  is  fluctuating  variation  due  to  environ- 
ment and  is  of  no  germinal  value. 

6.  The  F2  generation  is  more  variable  than  the  parents. 
When  sufficient  numbers  of  variates  were  studied  the  F2  showed 
a  range  of  variation  equal  to  the  combined  range  of  the  parents 
and  Fi. 

7.  In  the  two  crosses  studied  there  was  only  a  small  negative 
correlation  between  average  leaf  area  and  number  of  leaves  per 
plant.  This  indicates  that  leaf  number  and  average  leaf  area 
are  inherited  independently;  therefore  we  can  combine  the 
desirable  leaf  size  characters  of  one  variety  with  the  number 
of  leaves  of  another  form. 

8.  The  results  show  some  variation  in  the  correlation  be- 
tween height  of  plant  and  number  of  leaves.  Thus,  the  corre- 
lation coefficients  of  the  two  Fo  generations  of  the  cross  between 
(403x401)  were  +.342±.058  and  +.408±.036,  while  in  the 
F2  of  the  cross  between  (402  x  405)  the  correlation  coefficient 
was  -1-.814±.016. 

9.  There  was  found  a  large  positive  correlation  between 
length  and  breadth  of  leaf,  which  indicates  that  the  inheritance 
of  these  characters  depends  on  the  same  cause  or  series  of  causes. 

INTERPRETATION    OF   RESULTS. 

When  Mendel's  law  was  rediscovered  in  1900  it  was  generally 
believed  that  it  applied  only  to  a  few  isolated  cases  of  inheri- 
tance and  many  apparent  exceptions  were  cited.  By  a  better 
understanding  of  the  complexity  of  the  facts  or  by  simple 
extensions  of  the  Mendelian  notation,  most  of  these  apparent 
exceptions  have,  one  by  one,  been  shown  to  follow  the  law. 

The  inheritance  of  morphological  characters,  i.  e.,  form 
characters  such  as  size  of  stalk  and  leaf,  shape  of  leaf,  etc.,  which 
show  fluctuating  variability,  has  been  considered  by  many  to 
be  an  exception  to  the  Mendelian  rule.  By  fluctuating  varia- 
bility, as  used  in  this  paper,  we  mean  the  quantitative  fluctua- 
tions of  characters,  which  are  due  solely  to  environmental 
conditions,    soil,    climate,    etc.     While   such   fluctuations   have 


28  INHERITANCE  IN  NICOTIANA  TABACUM. 

no  value  in  inheritance  they  make  more  difficult  the  correct 
interpretation  of  experimental  data. 

Mendel's  principal  discovery  —  the  segregation  of  potential 
characters  in  the  germ  cells  of  hybrids  and  their  chance  recom- 
bination in  later  generations  —  has  given  a  logical  explanation, 
at  any  rate,  to  the  facts  which  we  now  have.  Whether  all 
characters  can  eventually  be  shown  to  be  Mendelian  is  of 
course  not  certain. 

The  results  above  given  are  statements  of  the  actual  behavior 
of  tobacco  plants  under  careful  observation.  The  interpre- 
tation of  these  results  which  follows  is  an  expression  of  opinion. 

For  the  characters  studied  there  is  a  much  greater  range 
of  variation  in  F2  than  in  Fi.  In  the  light  of  our  present  knowl- 
edge segregation  seems  to  be  the  best  interpretation  oj  this  fact. 

While  we  have  no  data  regarding  the  F3  generations  of  these 
crosses,  we  have  no  doubt  but  that  some  of  the  F2  t\^pes  will 
breed  true.  Our  reasons  for  this  belief  are  based  upon  some 
unpublished  results  of  the  study  of  the  inheritance  of  number 
of  leaves  per  plant  of  a  tobacco  cross,  which  show  that  in  gener- 
ations later  than  F2  both  intermediates  and  extremes  may 
breed  true.     How  then  may  the  tacts  be  explained? 

The  first  Mendelian  interpretation  of  variation  that  is  ap- 
parently continuous,  known  to  the  writer,  was  made  by  East 
(:10).  This  assumes  that  the  parent  plants,  for  the  character 
in  question,  differ  in  more  than  one  separateh^  inherited  unit 
or  gene.  Each  of  these  independent,  interchangeable  units, 
allelomorphic  to  its  own  absence,  is  capable  of  adding  to  the 
character,  and  the  heterozygous  condition  of  an}^  unit  is  half 
the  homozygous  condition. 

There  are  cases  of  color  inheritance  which  can  only  be  explained 
by  the  presence  of  two  or  more  separately  inherited  characters 
in  the  reproductive  cells.  Thus,  Nilsson-Ehle  (:09)  found  in 
one  case  two  definite,  independently  inherited  characters  for 
blackness  of  glumes  in  oats,  although  glume  blackness  in  other 
crosses  behaved  as  a  simple  Mendelian  mono-hybrid. 

Many  crosses  were  made  between  wheat  varieties  having  red 
and  white  seeds  and  in  all  but  one  of  these  the  F2  generation 
gave  the  ordinary  three-to-one  ratio.  But  a  cross  between 
an  old  red  seeded  wheat  from  the  north  of  Sweden  and  a  white 
variety  produced  only  red  seeds  in  a  total  progeny  of  78  F2 


INTERPRETATION  OF  RESULTS.  29 

plants.  The  expectancy  for  F2  if  the  parents  differed  in  three 
characters  for  red  would  be  63  reds  to  1  white.  The  progeny 
in  F3  of  these  78  F2  plants  gave  ratios  which  proved  that  he 
was  dealing  with  three  separately  inherited  characters  for  red. 

East  (:10)  found  that  in  certain  cases  there  were  two  indis- 
tinguishable independent  yellow  colors  in  the  endosperm  of 
maize.  Some  evidence  was  also  received  of  three  independent 
red  colors  in  the  pericarp  and  two  colors  in  the  aleurone  cells. 

East  and  Ha^^es  (:11),  in  a  study  of  inheritance  in  maize, 
gave  complete  results  of  a  number  of  observed  crosses  between 
yellow  and  white  varieties,  which  behaved  as  if  there  were  two 
separately  inherited  characters  for  yellow  color  in  the  endosperm 
of  maize,  either  of  which  could  produce  the  yellow  color.  Other 
crosses  were  mentioned,  between  yellow  and  non-yellow  (white) 
families,  which  behaved  as  simple  mono-hybrids.  Data  were 
given  of  a  number  of  flint-dent  crosses,  one  of  which  in  F)  gave 
about  one  pure  ear  in  every  sixteen,  while  one  cross  gave  an 
indication  of  a  higher  ratio.  Crosses  between  families  which 
showed  quantitative  differences  in  morphological  characters 
showed  wide  ranges  of  variability  in  F2  nearly  equal  to  the 
combined  range  of  the  parents. 

Emerson  (:10)  found  that  crosses  between  races  of  plants 
which  differ  in  sizes  and  shapes  have  increased  variability  in 
F2  as  compared  with  the  parent  or  Fi  forms.  His  data  were 
on  maize,  bean  and  gourd  crosses. 

Shull  (:11),  in  a  study  of  defective  inheritance  ratios  in 
Bursa  hybrids,  gave  results  which  indicate  the  presence  of  two 
genes,  each  of  which  is  independently  responsible  for  the  Bursa- 
pastoris-type  of  capsule.  The  Heegeri-type  appeared  only  when 
both  genes  were  absent. 

The  only  change  which  it  is  necessary  to  make  in  the  inter- 
pretation of  Nilsson-Ehle  and  East  for  inheritance  of  color 
characters,  in  order  to  have  the  hypothesis  fit  the  facts  for 
inheritance  of  fluctuating  plant  characters,  is  to  suppose  the 
heterozygous  condition  for  each  character  to  be  only  half  the 
homozygous  condition.  Thus  the  Fi  condition  for  any  character 
is  a  blend  between  the  parent  types,  instead  of  being  like  one 
.or  the  other  parent  forms  as  is  the  case  where  complete  domi- 
nance is  the  rule. 


30  INHERITANCE  IN  NICOTIANA  TABACUM. 

In  a  discussion  of  the  explanation  of  results  received  from 
crossing  certain  Linum  forms,  Miss  Tammes  (:11)  uses  a  similar 
interpretation  and  gives  an  excellent  discussion  of  this  hypothe- 
sis. The  number  of  individuals  studied  by  Miss  Tammes 
for  the  different  generations  is  very  small. 

Table  XIV  gives  the  theoretical  expectation  for  the  F2  genera- 
tion when  the  above  hypothesis  is  used.  The  first  column 
of  this  table  shows  the  number  of  units  or  genes  in  which  the 
P.  or  parent  forms  differ.  For  any  case  this  number  may  be 
represented  by  n. 

The  second  column  gives  the  numerical  proportion  of  the 
different  forms  until  the  parent  form  is  reached.  The  parent 
form  is  represented  by  P.  in  the  table.  These  classes  are  the 
coefficients  in  the  binominal  expansion  where  the  exponent 
is  twice  the  number  of  characters;  for  four  characters  the 
condition  would  be  represented  by  (a-Fb)",  the  coefficients  of 
this  expansion  giving  the  numerical  results  given  in  the  table 
for  four  characters. 

The  third  column  gives  the  number  of  individuals  which 
must  be  studied  in  order  to  have  an  even  chan  e  of  receiving 
some  individuals  in  each  class'.  This  number  is  equal  to  4^^ 
where  n  equals  the  number  of  unit  characters  in  which  the 
parents  differ. 

The  fourth  column  gives  the  number  of  homozygous  individ- 
uals which  may  be  expected  in  each  case.  This  number  equals 
2i^.  The  fifth  column  gives  the  per  cent,  of  homoz\^gous  in- 
dividuals which  may  be  expected  in  each  case. 

In  order  to  understand  this  complex  class  of  results  we  will 
discuss  a  specific  case.  Suppose,  for  example,  we  are  dealing 
with  number  of  leaves  per  plant  in  tobacco  crosses  and  that 
both  parents  of  a  certain  cross  are  pure  for  the  same  basal 
condition  of  twenty  leaves  per  plant  and  that  one  -parent  has 
in  addition  some  inherited  properties  which  result  in  a  produc- 
tion of  twenty-six  leaves  per  plant.  Let  us  suppose  this  con- 
dition due  to  three  interchangeable,  allelomorphic  character 
pairs,  each  inherited  separately,  and  that  the  heteroz^'gous 
condition  is  half  the  homozygous  condition.  If  we  follow  the 
usual  Mendelian  method  and  represent  the  presence  of  our 
three  characters  by  A,  B  and  C,  and  their  absences  by  a,  b  and 
c,  we  get  a  condition  in  Fi  of  AaBbCc,  or  23  leaves. 


X 

pq 

< 


..  ,   "2 

O        (M       , 

^J   txO  3 

IC        (M        CO 

C  >;^'d 

IC        (M        ^         lO 

u  S-r 

CJ   o   > 

O        »0        (M        CO        CO        i-H 

^  6^ 

lO        (M        T-H 

f^i.5 

S^ 

^    O    rt 

O   M  3 

c  N-rca 

C^        "*        GO        CO        (M        -^ 
^        CO        ^ 

o  c 

jz!'- 

CTj 

rt 

■*        CO        ^        CO        ^        CO 

^      CO      LO      (N      c; 

iM        O        O 

Z^ 

c 

•r-l 

^0, 

-flnS 

Uj 

-f^S        § 

s 

^1 

o 

^C.00       -       1 

c 

^PhO        2S        (M        C55 

ie 

"-^             T-H             T}^ 

Q 

1^       (--J        O        C5 

.^ 

-^        (M        t- 

-rJ 

"o 

O         O         (M          -^ 

o.      CO      g      g      o      g 

'-p 

-A.^     2     §     2     § 

o 

•^        (M        t^ 

o 
1-. 

f-yn         O          LO 
rHflnCO        ^        (M        Ci 

Oh 

^^           T-H           -^ 

rf 

CJ 

LO           O 
r-HpLnOO           ^           W 

z 

-OhS        § 

-0.^ 

^PLh 

C        t:?   t« 

•-^.ti  °  s 

<u  c  "2  d 

y  s  3  o 

0)^   o     .  f= 

rH           (M           CO           'IJH            "O           CO 

^°2f^ 

cC  o  erf  0) 

Q^-g^ 

32 


INHERITANCE  IN  NICOTIANA  TABACUM. 


In  Fo  we  may  expect  a  range  of  variability  shown  for  three 
characters  in  the  table.  In  order  to  understand  the  gametic 
differences  in  Fo  we  must  study  the  gametic  formula  of  these 
classes  so  that  we  may  understand  their  future  expectations 
in  breeding.     The  conditions  are  as  follows : 

will  breed  true  in  F3. 


1  AABBCC 

=  26  leaves. 

2  .AaBBCC 

=  25 

u 

2  AABbCC 

=  25 

a 

2  AABBCc 

=  25 

a 

4  AaBbCC 

=  24 

a 

4  AaBBCc 

=  24 

a 

4  AABbCc 

=  24 

a 

8  AaBbCc 

=  23 

a 

1  AABBcc 

=  24 

11 

2  AaBBcc 

=  23 

a 

2  AABbcc 

=  23 

a 

4  AaBbcc 

=  22 

ii 

1  AAbbCC 

=  24 

a 

2  AabbCC 

=  23 

a 

2  AAbbCc 

=  23 

a 

4  AabbCc 

=  22 

a 

1  aaBBCC 

=  24 

a 

2  aaBbCC 

=  23 

ii 

2  aaBBCc 

=  23 

11 

4  aaBbCc 

=  22 

li 

1  AAbbcc 

=  22 

ii 

2  Aabbcc 

=  21 

li 

1  aaBBcc 

=  22 

a 

2  aaBbcc 

=  21 

li 

1  aabbCC 

=  22 

11 

2  aabbCc 

=  21 

11 

1  aabbcc 

=  20 

a 

will  breed  true  :n  F3 


will  breed  true  in  F3 


will  breed  true  in  F2 


will  breed  true  in  F3 


will  breed  true  in  F3 


will  breed  true  in  F3 


will  breed  true  in  F3 


Thus  we  see  that  out  of  a  total  of  sixty-four  individuals  we 
may  expect  eight  to  breed  true,  and  of  these  eight,  one  will 
breed  true  for  each  parent  form,  or  for  twent}^  and  twenty-six 
leaves,  three  will  breed  true  for  twenty-two  leaves,  and  there 
for  twenty-four  leaves. 

The  remainder  w^ll  break  up  again  in  F3  although  some  will 
show  a  greater  variation  than  others.     Thus,  according  to  our 


INTERPRETATION  OF  RESULTS.  33 

hypothesis,  AaBbCc  and  AABbcc  represents  conditions  of 
twenty-three  leaves.  The  form  AaBbCc  will  give  a  range  of 
variation  in  Fs  equal  to  that  of  Fo,  while  the  other  gametic 
formula,  AABbcc,  will  produce  one-half  its  forms  with  twenty- 
three  leaves,  one-fourth  each  with  twenty-two  and  twenty- 
four  leaves 

The  difficulty  of  correctly  interpreting  the  method  of  inher- 
itance of  such  plant  characters  is  greatly  increased  by  fluctua- 
tions due  to  environmental  conditions. 

In  the  first  cross  studied,  (405  x  400),  Table  III,  the  parents 
do  not  probably  differ  in  more  than  one  character  pair,  for 
number  of  leaves  per  plant,  as  the  range  of  variability  is  only 
increased  by  two  or  three  classes,  due  to  crossing. 

The  average  difference  in  the  parents  of  the  cross  (403  x  401), 
Table  IV,  is  about  ten  leaves.  According  to  the  hypothesis, 
each  character  in  a  homozygous  condition  adds  two  leaves  and 
the  heterozygous  condition  is  half  the  homozygous.  On  this 
basis  the  parents  differ  in  five  characters.  The  numerical  pro- 
portions given  for  five  characters  in  Table  XIV  are  very  similar 
to  the  classes  received  in  F2.  The  number  of  classes  for  the 
cross  (403  X  401)-3,  B,  of  which  1,632  plants  were  counted,  is 
■eighteen,  while  the  number  of  classes  for  fiA^e  characters,  Table 
XIV,  is  eleven.  Thus  the  range  of  variability  in  F2  which  is  not 
■explained  by  our  hypothesis  is  seven  classes.  This  is  about 
the  same  range  as  is  ordinarily  received  in  the  parent  forms  due 
to  fluctuating  variability. 

Considering  now  our  third  family,  (402  x  405) ,  we  observe 
that  the  parent  forms  each  had  about  the  same  mode  for  num- 
ber of  leaves,  yet  in  Fo  there  was  a  large  range  of  variability. 
This  condition  is  very  easily  explained  by  our  hypothesis.  If 
we  suppose  each  of  the  parent  forms  to  be  pure  for  the  same 
basal  condition  of  sixteen  leaves,  their  gametic  condition  to  be 
16AABB  and  16CCDD,  and  none  of  these  factors  are  allelomor- 
phic  to  each  other,  we  will  receive  a  much  greater  range  in  F2 
than  in  Fi.  In  this  connection  it  is  interesting  to  note  that  in 
East's  original  interpretation  of  the  inheritance  of  variations 
•of  this  type  it  was  predicted  that  such  a  result  should  occur  if  the 
hypothesis  was  correct.  That  we  are  able  to  give  a  case  which 
shows  such  results  seems  a  further  proof  of  the  correctness  of 
the  interpretation. 


34  INHERITANCE  IN  NICOTIANA  TABACUM. 

In  the  cross  of  (403  x  401),  Table  VI,  it  seems  very  probable 
that  we  are  dealing  with  a  condition  of  at  least  five  character 
pairs  for  difference  in  average  leaf  area.  This  explains  why 
there  was  so  small  a  range  of  variability  in  F2,  as  only  150 
plants  were  studied.  According  to  Table  XIV,  when  the  plants 
differ  in  a  large  number  of  character  pairs  and  only  a  limited 
progeny  is  grown  in  F2,  the  expectancy  is  that  the  greater  part 
of  the  variates  will  occupy  an  intermediate  condition. 

In  the  study  of  leaf  area  for  the  cross  of  (402  x  405),  Tables  XI, 
XII  and  XIII,  the  difference  in  leaf  size  characters  for  the  parent 
varieties  seems  chiefly  to  be  one  of  length.  Results  indicate 
that  these  types  did  not  differ  in  more  than  two  character 
pairs. 

Conclusions. 

Our  results  are  entirely  in  accord  with  the  Mendelian  inter- 
pretation of  quantitative  characters,  such  as  the  size  of  various 
plant  organs,  by  the  hypothesis  that  a  multiplicity  of  factors 
exists,  each  independently  inherited  and  capable  of  adding  to 
the  character,  the  heterozygous  condition  being  half  the  homo- 
zygous. The  difficulty  of  correctly  determining  the  exact  number 
of  factors  in  any  case  is  greatly  increased,  however,  by  the 
presence  of  fluctuations  which,  although  of  no  germinal  value, 
obscure  the  action  of  heritable  factors.  Moreover,  some 
characters  seem  independently  inherited,  others  closely  corre- 
lated in  inheritance  and  still  others  partially  correlated.  These 
facts  make  the  analysis  of  pedigree  culture  data  yet  more 
difficult. 

It  has  been  stated  by  certain  critics  that  by  the  use  of  a 
number  of  factors  or  by  the  juggling  of  factors  that  any  condi- 
tions could  be  explained.  Whether  we  use  the  factorial  method 
or  not,  however,  does  nor  change  the  actual  results  of  experi- 
mental work.  An  examination  of  the  data  reported  in  this 
paper  will  convince  the  reader  that  the  Fo  generation,  for  each 
character  studied,  is  more  variable  than  the  Fi  and  that  when 
a  large  number  of  individuals  are  examined  the  F2  generation 
has  a  range  of  variation  equal  to  the  combined  range  of  the 
parents.  The  results  seem  most  easily  explained  by  segrega- 
tion, in  which  a  number  of  factors  are  concerned. 


CONCLUSIONS.  35 

The  characters  which  have  been  studied  and  upon  which  these 
conclusions  depend  are;  number  of  leaves  per  plant,  height  of 
plant,  average  area  of  leaf,  length  and  breadth  of  leaf. 

Suggestions   to    the   Economic   Plant    Breeder  from    the    Results 
Reported  in  this  Paper. 

The  value  of  using  inbred  tobacco  seed  for  the  commercial 
crop  has  been  previously  discussed  in  our  Station  reports. 
By  protecting  the  seed-head  from  cross  pollination,  seed  from 
the  most  desirable  plants  may  be  obtained.  The  results  of 
the  different  generations  of  the  parent  varieties  shown  in  this 
paper  confirm  previous  conclusions  and  prove  that  the  progeny 
of  inbred  tobacco  varieties  are  very  uniform  for  the  characters 
studied.  Thus  by  selection  the  grower  can  obtain  the  better 
types  and  by  breeding  from  these  produce  uniform  crops. 
Because  the  tobacco  plant  is  so  noticeably  affected  by  conditions 
of  fertility  and  differences  of  soil,  the  selection  of  a  desirable 
type  which  will  breed  true  is  not  so  easy  as  it  would  seem.  It 
is  necessary  to  make  a  number  of  selections  from  desirable 
types  and  test  their  value  the  following  year  by  growing  them  in 
row  selections.  Those  which  breed  true  to  the  desired  type 
have  proved  their  abilit}^  to  reproduce  their  kind. 

The  production  of  new  improved  forms  by  crossing  is  not 
a  simple  matter  and  should  not  be  undertaken  by  anyone  who 
has  not  a  knowledge  of  the  particular  qualities  which  the  trade 
demands.  .  A  good  wrapper  tobacco  must  have  certain  charac- 
teristics in  order  to  be  of  any  value;  of  these,  burn,  flavor,, 
texture,  color  when  cured,  etc.,  are  good  examples. 

As  to  the  field  characters  of  tobacco,  we  may  give  a  plan 
which  should  be  followed  when  attempting  the  improvement  of 
tobacco  by  hybridization. 

CrossQs  should  be  made  between  inbred  types  of  known  value. 
This  method  insures  the  elimination  of  unselected  strains. 
When  this  plan  is  followed  we  may  rest  assured  that  the  Fi 
generation  will  be  uniform.  Only  a  few  plants  need  to  be 
grown  of  this  generation,  as  none  will  breed  true  in  F2.  Increased 
vigor  is  obtained  in  Fi,  the  cross,  as  a  rule,  growing  more  rapidly 
than  thejparents.     Observations  on  the  cured  leaf  of  several 


36  INHERITANCE  IN  NICOTIANA  TABACUM. 

Fi  crosses  have  convinced  the  writer  that  the  leaves  of  this 
generation  are  of  ver}^  poor  quaHty. 

The  F 2  generation  should  consist  of  from  5,000  to  6,000  plants, 
as  this  is  the  generation  in  which  there  will  be  a  breaking  up  into 
different  types.  Of  this  generation,  seed  should  be  saved  from 
those  types  which  give  promise  of  value  and  should  be  grown 
in  row  selections  the  following  year.  When  a  type  gives  promise 
of  commercial  value  in  the  row  test  a  larger  amount  should  be 
grown,  and  after  being  harvested,  cured  and  fermented,  tested 
for  quality. 

LITERATURE  CITED. 
East,  E.  M. 

:10     A   Mendelian   Interpretation   of   Variation   that  is   Apparently 

Continuous. 

Amer.  Nat.  44:65-82. 
:11      The  Genotype  Hypothesis  and  Hybridization. 

Amer.  Nat.  45:160-174. 

East,  E.  M.  and  Hayes,  H.  K. 
:11      Inheritance  in  Maize. 

Conn.  Expt.  Sta.  BuU.  167:1-142. 

Emerson,  R.  A. 

:10     Inheritance  of  Sizes   and  Shapes  in  Plants. 

Amer.  Nat.  44:739-746. 
:11      Genetic   Correlation   and   Spurious   Allelomorphism   in   Maize. 
Nebraska  Expt.  Sta.  Rep.  24:58-90. 
Johannsen,  W. 

:07     Does  Hybridization  Increase   Fluctuating  Variability? 

Report     Third     Inter.     Con.     on     Genetics,     London, 
Spottiswoode. 
Love,  H.  H. 

:11      Studies  on  Variation  in  Plants. 

Cornell  Expt.  Sta.  Bull.  297:593-677. 

Nilsson-Ehle,  H. 

:09     Kreuzungsuntersuchungen  an  Hafer  und  Weizen. 

Lunds  Universitets    Arsskrift,    N.    F.    Afd.    2,     Bd.    5, 
Nr.  2:1-122. 
Shull,  G.  H. 

:11      Defective    Inheritance-Ratios    in    Bursa    Hybrids. 

Verhandl.     Naturf.    Ver.     Briinn,    Bd.    49:1-12     (The 
Mendel  Festband). 
Tammes,  T. 

:11     Das    Verhalten    fiuktuierend    variierender    Merkmale    bei    der 
Bastardierung. 

Rec.    Trav.    Bot.    Neerl.,    Vol.    VIII,    Livr.    3:201-288. 


CORRELATION  TABLES. 


37 


TABLE    XV. 

CORRELATION    BETWEEN    NO.    OF  LEAVES    AND   HEIGHT   OF    PLANT   OF 
NO.    401,    BROADLEAF. 


No.  of  Leaves. 


Ph  <d 


17 

18 

19 

20 

21 

22 

44 

1 

47 

3 

1 

50 

7 

10 

3 

53 

2 

13 

17 

11 

1 

56 

1 

5 

21 

14 

3 

1 

59 

1 

10 

8 

1 

1 

62 

1 

6 

4 

2 

1 

65 

1 

3 

30 

65 

41 

7 

4 

1 

4 
20 

44 

45 

21 

14 

1 

150 


No.  of  Leaves.  Height  of  Plants. 

A.       =19.2    ±.053  A.       =55.0    ±.212 

S.  D.  =   0.96  ±.037  S.  D.  =   3.85  ±.150 

Coef.  Cor.  =  +.368  ±.048 


TABLE    XVL 

CORRELATION    BETWEEN    NO.    OF   LEAVES   AND    HEIGHT   OF   PLANT 
OF    NO.    403,    SUMATRA. 


No.  of  Leaves. 


ffi 


24 

25  26 

27 

28 

29 

30  31 

6"? 

1 
1 

65 

68 

1  .  . 

1  2 
..  6 
1  5 

'4 

2 

7 

'4 

6 

17 

71 
74 

2 

1 

'3  '.'. 

77 

6 
3 
1 

11 
5 
2 

1 

11 

8 
6 

8  1 

11  5 

5  2 

.  .  .  .  1 

80 

83 

86 

2 

3  13 

23 

46 

28 

27  8  ! 

1 

2 
11 
16 
34 
37 
32 
16 
1 
150 


No.  of  Leaves. 
A.       =28.3    ±.082 
S.  D.  =    1.49  ±.058 

Coef.  Cor. 


Height  of  Plants. 
A.       =76.1    ±.251 
S.  D.  =   4.55  ±.177 
+  .631  ±.033 


38 


INHERITANCE  IN  NICOTIANA  TABACUM. 


TABLE    XVII. 

CORRELATION    BETWEEN    NO.    OF   LEAVES    AND    HEIGHT    OF    PLANT 
OF    NO.    (403   X  401),    SUMATRA   X    BROADLEAF. 


No.  of  Leaves. 


-iJl— I 

'S 


K 


19 

21  22  23 

24 

25  26 

50 
59 
6? 

1 

'  '  1  '.'. 
....   1 

2 
4 
8 
13 
6 
5 

'l  '.  '. 

2  1 

3  1 
5  2 

11  2 
5  2 
1  2 
1  .. 

65 
68 
71 

74 

77 

1 

.  .  7   2 

1  5   12 

2  5  18 
.  .  3   8 

80 

83 

2 

3  21  47 

38 

29  10 

No.  of  Leaves. 
A.       =23.6    ±.072 
S.  D.  =    1.30 ±.051 

Coef.  Cor. 


1 
1 

4 
17 
30 
45 
30 
18 
3 
1 

150 


Height  of  Plants. 
A.       =70.8    ±.250 
S.  D.  =   4.54  ±.177 
+.406  ±.046 


TABLE    XVIII. 

CORRELATION    BETWEEN    NO.    OF   LEAVES    AND    HEIGHT   OF   PLANT 
OF    (403  X  401  )-l,    SUMATRA   X    BROADLEAF,    F2. 


PU 


'S 


35 

38 
41 
44 
47 
50 
53 
56 
59 
62 
65 
68 
74 


No.  of  Leaves. 
19  20  21  22  23      24  25  26  27  28  30 


'. '.   2 

1 

3 
2 
2 
2 

1 

1 
2 

3 
3 

1 
1 
1 
4 
3 
3 

1  .  . 

2  1 

1  .  . 

2  2 
4  3 

2 
2 

1 

2 

1    '.. 

'l    '/. 

'.  '.     3 
1  1 

.  .   1 
..   1 

1 

3 
2 

1  3 
3  5 

..   3 

2  1 

1 
3 

2 

i 

1 
1 

'i 

I    .  . 
.  .      1 

1  .  . 

2  '.'. 

1 

1  8 

LO  ] 

11 

19 

16  IS 

11 

6 

6  1 

No.  of  Leaves.. 
A.       =23.8    ±.146 
S.  D.  =   2.24  ±.103 

Coef.  Cor. 


+  .342: 


1 

3 

3 

8 

11 

19 

20 

11 

16 

7 

4 

3 

107 


Height  of  Plants. 
A.  =53.1  ±.471 
S.  D.  =  7.22  ±.333 
.058 


CORRELATION  TABLES. 


39 


TABLE    XIX. 

CORRELATION    BETWEEN    NO.    OF  LEAVES    AND    HEIGHT   OF    PLANT   OF 
(403  X  401  )-4,    SUMATRA   X   BROADLEAF,    F2. 

No.  of  Leaves. 


9 
23 
38 
28 
49 
34 
27 
22 

7 

241 


s 


18 

19 

20 

21 

22 

23 

24 

25 

26  27 

28  29 

38 

3 

5 

2 

1 

1 

7 

1 
5 

2 

"4 

41 

1  .  . 

44 

1 

10 

11 

11 

2 

2 

1 

47 

2 

3 

5 

5 

5 

6 

1 

1 

50 

2 

4 

8 

12 

12 

6 

3 

2 

53 

2 

7 

9 

5 

6 

4 

1  .  . 

56 

3 

7 

9 

2 

4 

1  1 

59 

2 

2 

1 

10 

2 

1 

2  1 

62 

1 

1 

1 

2 

2 

65 

1 

2 

1  .  . 

5 

16 

30 

50 

52 

41 

22 

15 

■7  1 

1   1  1 

No.  of  Leaves. 
A.       =22.0    ±.083 
S.  D.  =    1.91  ±.061 


Height  of  Plants. 
A.       =49.9    ±.276 
S.  D.  =   6.36  ±.202 


Coef.  Cor.  =  +.408  ±.036 
TABLE    XX. 

CORRELATION  BETWEEN  NO.  OF  LEAVES  AND  AVERAGE  AREA  OF 
LEAVES  OF  NO.  401,  BROADLEAF. 


No.  of  Leaves. 


1-4  lA 


<  ^ 


17 

18 

19 

20 

21 

22 

5 

1 

1 

1 

3 

6 

4 

3 

1 

8 

7 

7 

11 

10 

3 

31 

8 

2 

4 

15 

5 

2 

2 

30 

9 

4 

18 

9 

2 

33 

10 

1 

8 

10 

8 

27 

11 

3 

2 

2 

7 

12 

3 

4 

2 

9 

13 

1 

1 

14 

i 

1 

3 

30 

65 

41 

7 

4 

150 

No.  of  Leaves. 
A.       =19.2    ±.053 
S.  D.=   0.96  ±.037 

Coef.  Cor.  = 


Aver.  Area  of  Leaves. 
A.       =8.7    ±.093 
S.  D.  =1.70  ±.066 
-.165  ±.054 


40 


INHERITANCE  IN  NICOTIANA  TABACUM. 


TABLE    XXI. 

CORRELATION    BETWEEN    NO.    OF   LEAVES    AND    AVERAGE    AREA    OF 
LEAVES    OF    NO.    403,    SUMATRA. 


> 

CD 

o  g     2 
gQ     3 

No.  of  Leaves 
24  2.5  26  27  28 

29  30  31 

....      1     2     3 
2     3     9  15  26 

1     2    .. 
16  22     7 

....      3     6  16 
1 

10     3     1 
1    .  .    .  . 

M  ^ 


9 
100 

39 
2 


2     3   13  23  46      28  27     8    150 


No.  of  Leaves. 
A.       =28.3    ±.082 
S.  D.  =    1.49  ±.058 

Coef .  Cor.  = 


Aver.  Area  of  Leaves. 
A.       =3.23  ±.031 
S.  D.  =0.57  ±.022 
-.008  ±.055 


TABLE    XXII. 

CORRELATION  BETWEEN  NO.  OF  LEAVES  AND  AVERAGE  AREA  OF 
LEAVES  OF  NO.  (403  X  401),  SUMATRA  X  BROADLEAF,  Fi. 


No.  of  Leaves. 
19  21  22  23   24  25  26 


^S    4 

1 

2 

2 

5 

??Q    5 

4 

13 

7 

5 

3 

32 

u   .    6 

1 

6 

13 

13 

9 

4 

46 

1 

2 

4 

10 

16 

11 

44 

U)c     8 

1 

6 

8 

2 

2 

19 

r'     9 

1 

2 

1 

4 

2  3  21  47   38  29  10  150 


No.  of  Leaves. 
A.       =23.6    ±.072 
S.  D.  =    1.30  ±.051 

Coef.  Cor. 


Aver.  Area  of  Leaves. 
A.       =6.35  ±.062 
S.  D.  =1.13  ±.044 
-.226  ±.052 


CORRELATION  TABLES. 


41 


TABLE   XXIIL 

CORRELATION  BETWEEN  NO.  OF  LEAVES  AND  AVERAGE  AREA  OF 
LEAVES  OF  (403  X  401)-1,  SUMATRA  X  BROADLEAF,  Fo. 

No.  of  Leaves. 


can 

<;  cr 

C/2 


19  20  21  22 

23 

24  25  26 

27  28  30 

3 

4 
5 

..   1  ..  .  . 

..112 

116  2 

6 

5 

.  .   1  .  . 
4  2  4 
4  4  1 

'2  '1  'i 

1  4  .. 

6 

7 
8 

..   2  ..   6 
..   2  2  .. 
..Ill 

4 
3 

1 

4  8  4 
2  2  2 
2 

3  1.. 

q 

..  i 

1  8  10  11 

19 

16  18  11 

6  6  1  i 

2 
24 
29 
32 
13 

6 

Ji^ 

107 


No.  of  Leaves. 
A.       =23.8    ±.146 
S.  D.  =   2.24  ±.103 

Coef.  Cor. 


Aver.  Area  of  Leaves. 
A.        =5.58  ±.080 
S.  D.=  1.23  ±.057 
-.124  ±.065 


TABLE    XXIV. 

CORRELATION  BETWEEN  NO.  OF  LEAVES  AND  AVERAGE  AREA  OF 
LEAVES  OF  (403  X  401)-4,  SUMATRA  X  BROADLEAF,  F2. 


!> 


No.  of  Leaves. 
18  19  20  21  22      23  24  25  26  27  28  29 


3 
4 
5 

..   1  . .   1  2 

.  .   1  5  6  10 

1  6  12  18  18 

1  7  6  17  16 

2  15  6  6 
1  .  .   2  2  .  . 

1  2  .. 

11  6  3 

12  8  3 

1  1 
3  .. 
1  .  . 

i  i 

6 

7 
8 

13  5  6 
3  1  2 
1  .  .   1 

1  .  . 
1  .  . 

5  16  30  50  52 

41  22  15 

7  1 

1  1 

No.  of  Leaves. 
A.       =22.0    ±.083 
S.  D.  =   2.24  ±.103 

Coef.  Cor. 


.076: 


9 

47 
79 
72 

27 

7 

241 


Aver.  Area  of  Leaves. 
A.       =5.34  ±.048 
S.  D.  =1.11  ±.035 

:.043 


42 


INHERITANCE  IN  NICOTIANA  TABACUM. 


TABLE    XXV. 

CORRELATION    BETWEEN   AVERAGE    WIDTH    OF   LEAVES    AND    AVERAGE 
LENGTH    OF   MIDRIB    OF    NO.    401,    BROADLEAF. 

Aver.  Width  of  Leaves  in  Cms. 


h- 1  "^ 

< 


18  21 

24  27  30  33 

8Q 

4   1 

5 

42 
45 

48 

4   7 

.   27 

8 

1   ..   . 

7 

25   5  .  .   . 

12 

34 

38 

51 

54 

57 

'.      i 

18  14   1   . 
6   9  ..   . 
3   3 

i 

33 
16 

7 

60 
68 

12   1. 

1 

4 
1 

8  44 

57  34   5 

2 

150 

Aver.  Width  of  Leaves. 
A.       =23.8    ±.164 
S.  D.  =   2.97±.116 

Coef.   Cor. 


Aver.  Length  of  Leaves. 
A.       =48.7    ±.258 
S.  D.  =   4.69  ±.183 
+.684  ±.029 


TABLE    XXVI. 

CORRELATION    BETWEEN   AVERAGE    WIDTH   OF   LEAVES    AND   AVERAGE 
LENGTH    OF   MIDRIB    OF    NO.    403,    SUMATRA. 

Aver.    Width    of    Leaves   in    Cms. 


12 

15 

18 

21 

24 

5 

5 

27 

14 

33 

7 

1 

30 

2 

50 

18 

2 

33 

2 

10 

36 

i 

21 

90 

35 

4 

^o 


M  > 

< 

Aver.  Width  of  Leaves.  Aver.  Length  of  Leaves. 

A.       =15.4    ±.111  A.       =28.8    ±.125 

S.  D.  =   2.03  ±  069  S.  D.  =   2.27  ±.088 

Coef.  Cor.  =  +.497  ±.041 


CORRELATION  TABLES. 


45 


TABLE    XXVIL 

CORRELATION  BETWEEN  AVERAGE  WIDTH  OF  LEAVES  AND  AVERAGE  LENGTH 
OF  MIDRIB  OF  NO.  (403  X  401),  SUMATRA  X  BROADLEAF.  Fi. 


Aver.  Width  of  Leaves  in  Cms. 


L5     18      21     24     27 


30 
88 

1 
4 

2 

1 
6 

^u 

36 

22 

4 

26 

X^ 

39 
42 

13 

34 

3 

50 

SoP 

26 

20 

46 

S  ^ 

45 

2 

14 

1 

17 

48 

3 

1 

4 

< 

5 

37 

66 

40 

2 

150 

Aver.  Width  of  Leaves. 
A.       =20.9    ±.138 
S.  D.  =   2.51  ±.098 

Coef.  Cor. 


Aver.  Length  of  Leaves. 
A.       =40.0    ±.187 
S.  D.  ='  3.39  ±.132 

+  .818  ±.018 


TABLE    XXVIIL 

CORRELATION  BETWEEN  AVERAGE  WIDTH  OF  LEAVES  AND  AVERAGE 
LENGTH  OF  MIDRIB  OF  (403  X  401)-1,  SUMATRA  X  BROADLEAF,  F2. 

Aver.  Width  of  Leaves  in  Cms. 


^O 


< 


12 

15 

18 

21 

24 

27 

30 

7 

33 

1 

11 

5 

36 

4 

19 

3 

39 

1 

11 

20 

1 

42 

5 

5 

4 

i 

45 

1 

2 

2 

48 

2 

2 

1 

23 

41 

32 

9 

1 

7 

17 
26 
33 
15 
5 
_^ 
107 


Aver.  Width  of  Leaves. 
A.       =18.8    ±.186 
S.  D.=   2.85  ±.131 

Coef. 


Cor.  =  +.737 


Aver.  Length  of  Leaves. 
A.       =37.4   ±.275 
S.  D.  =   4.22 ±.195 

t.030 


44 


INHERITANCE  IN  NICOTIANA  TABACUM. 


TABLE    XXIX. 

•CORRELATION  BETWEEN  AVERAGE  WIDTH  OF  LEAVES  AND  AVERAGE  LENGTH 
OF    MIDRIB    OF    (403  X  401)-4,    SUMATRA   X    BROADLEAF,    F2. 

Aver.  Width  of  Leaves  in  Cms. 


^O 


12     15 

18 

21 

24 

27 

1 

1 

30 

2       6 

1 

9 

33 

.  .      19 

14 

33 

36- 

7 

52 

3 
36 

1 

62 

39 

46 

83 

42 

7 

25 

5 

37 

45 

4S 

1 

8 
1 

6 

15 
1 

2     33  121      73     12  i  241 


Aver.  Width  of  Leaves.  Aver.  Length  of  Leaves. 

A.       =18.8    ±.102  A.       =37.9    ±.160 

S.  D.  =   2.34  ±.074  S.  D.  =   3.69  ±.117 

Coef.  Cor.  =  +.761  ±.018 


TABLE    XXX. 

CORRELATION   BETWEEN    NO.    OF   LEAVES    AND    HEIGHT    OF    PLANT 
OF    (402   X   405)-l,    HAVANA   X   CUBAN,    Fz- 

No.  of  Leaves. 


1415  161718  19  20 

21  22  23  24  25  26  27  28  29  30  31  32  33 

41 

2  .  .     1    1 

44 

1  .  . 

' 

47 

.  .     2    1  .  .     1    1  .  . 

50 
53 
56 
59 
62 

.  .     2    1  .  .     1  .  .     1 

1  ..    3    3    6    3    3 

....     23533 

4    3    5 

2    4    7 

....     1  

1  2 

2  ..     1 

3  2    1    1 

5    3    3    2    1 

65 

68 

1    1    1    9 

2    2 

3  8    2    3 

4  3    2    1    1 

42    3    2..     1 

1    5    4    2    1    2    1    1 

1....    2    2..     1....     1..     1.. 

2  .  .  .  .     1 1 

71 

74 

77 

80 

83 

1  .  .     1  .  .  .  .'   1  

86 

1    1  .. 

3    4    8    8  2018  30 

24  25  17  16    5    4    3    1    1    1    1    2    1 

No.  of  Leaves. 
A.       =20.9    ±.161 
S.  D.  =   3.31  ±.114 

Coef.  Cor. 


Height  of  Plants. 
A.       =62.9    ±.449 
S.  D.  =   9.23  ±.318 
+.786  ±.023 


4 

1 

5 

6 

22 

19 

19 

27 

28 

15 

12 

17 

8 

4 

3 

2 


192 


CORRELATION  TABLES. 


45- 


TABLE    XX  XL 

CORRELATION  BETWEEN  NO.  OF  LEAVES  AND  AVERAGE  AREA  OF  LEAVES 
OF  (402  X  405)-l,  HAVANA  X  CUBAN,  F2. 


No.  of  Leaves. 


o  o 


u 

> 
< 


14  15  16  17  18  19  20 

21  22  23  24  25  26  27  28  29  30  31  32  33 

3 
4 
5 
6 

1 

12  2 

'1  '1  1  '2  3  2  5 

1  ..  1  ..  6  3  3 

1  .  .  1 

....  2  .  .  1  1 1  .  . 

3  6  2  2  2..  1..  1  

5  2  2  3  .  .  1  2  .  .  .  .  1  .  .  1  .  . 

7 

8 

9 

10 

11 

1112  2  4  9 
..  12  2  4  3  4 
....  2  .  .  444 
.  .  1  1  1  .  .  .  .  2 
1 

6  8  2  6  1....  1 1 

4  4  4  2..  2 1.... 

2  4  1  2  1 

1  1  1  1  .  . 

1  .  .  2 

1         .           

1? 

3  4  8  8  20  18  30 

24  25  17  16  5  4  3  1  1  1  1  2  1  , 

3 

10 

32 

31 

45 

33 

24 

9 

4 

1 

192 


No.  of  Leaves. 
A.       =20.9    ±.161 
S.  D.  =    3.31  =t. 114 

Coef.  Cor.  = 


Average  Area  of  Leaves. 
A.       =   6.96  ±.085 
S.  D.  =   1.76  ±.061 
.092  ±.048 


TABLE    XXXII. 

CORRELATION  BETWEEN  AVERAGE  WIDTH  OF  LEAVES  AND  AVERAGE  LENGTH 
OF    MIDRIB    OF    (402  X  405)-l,    HAVANA   X   CUBAN,    F2. 


Aver.  Width  of  Leaves  in  Cms. 


27 
30 
33 
36 
39 
42 

45 
48 
51 
54 


12  15  18     21      24     27     30 


1 

11 

.53.. 
.  3  13   2 
.  2  14  11 
.  . .  5  22 

8   ..   .. 

...   1  20 
7 

21   6   .  . 
15  11   1 

5   6  .. 

2   3   2 

1  11  37  62 

52  26   3 

Aver.   Width  of   Leaves. 
A.       =21.8    ±.170 
S.  D.  =   3.49  ±.121 

Coef.  Cor. 


8 
18 
28 
35 
48 
34 
11 
_J 
192 


Aver.  Length  of  Leaves. 
A.       =43.2    ±.247 
S.  D.  =    5.28  ±.182 
+  .814±.016 


PLATE 


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PLATE    II. 


a.     Average  middle  leaf  of  No.  402,  Havana  at  left,  of  No.  405, 
Cuban  at  right  and  Fi  in  center. 


b.     Some  Fo  middle  leaves  of  cross  between  No.  402,  Havana  and 
No.  405,  Cuban. 


PLATE    III. 


to      I 
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